In vehicles having no internal combustion engine, such as electric vehicles and fuel cell vehicles, the heat of the engine cannot be used as a heat source during heating operation. For this reason, in this type of vehicle, an air-conditioning apparatus that performs heating operation using a heat pump cycle is used. In many air-conditioning apparatuses using a heat pump cycle, a refrigerant flow passage is switched between cooling operation and heating operation.
However, in an air-conditioning apparatus that switches a refrigerant flow passage between cooling operation and heating operation, the number of various incidental components such as pipes, valves, and fittings increases, and therefore the increase in product cost and the increase in weight are likely to be caused, and, in addition, there is fear that the air-conditioning performance is worsened, for example, by the increase in flow resistance of refrigerant.
For this reason, as an air-conditioning apparatus that can cope with this, an air-conditioning apparatus is devised in which a heat exchange unit in which refrigerant is circulated between a condenser and an evaporator is disposed in a casing, and air passing through the casing and supplied to a vehicle interior exchanges heat selectively with the condenser or with the evaporator according to the operation mode (see, for example, Japanese Unexamined Patent Application Publication No. 2013-180648). In the heat exchange unit of this air-conditioning apparatus, the refrigerant outlet of the condenser is connected to the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator is connected to the suction part of a compressor, and the discharge part of the compressor is connected through an expansion valve to the inlet of the evaporator.
However, in the case of the air-conditioning apparatus described in Japanese Unexamined Patent Application Publication No. 2013-180648, there is a problem in that refrigerant compressed in the compressor condenser not effectively cooled (heat-radiated) in the condenser, and the refrigerant is hard to subcool before the refrigerant is expanded in the expansion valve. In this case, the evaporator is poorly supplied with subcooled refrigerant, and there is room for improvement in terms of air-conditioning efficiency.